Wheelchairs are designed in both non-folding and folding designs. The present invention will be described for exemplary purposes in conjunction with a folding wheelchair. It is to be understood that the unique suspension system of the present invention can be incorporated into either a non-folding or a folding wheelchair and the description of the suspension system in conjunction with a folding wheelchair is not intended to be limiting.
Folding wheelchairs generally comprise a rigid frame with right and left closed frame members and a pair of large wheels rotatably mounted thereon. This arrangement allows the occupant to propel the chair using the wheels. The right and left hand closed frame members, in a folding wheelchair, are usually connected by two diagonally-extending cross-tubes which can be scissored together to fold the chair. While these folding wheelchairs have significantly increased the portability of wheelchairs, they have done so at the cost of sacrificing frame strength and frame stability.
In addition, the large wheels which are rotatably mounted on the rigid frames are generally mounted directly to the rigid frames. This creates a system which is uncomfortable and somewhat unstable when traveling over an uneven terrain. There have been some attempts at overcoming this problem. Assignee's U.S. Pat. No. 4,861,056 the disclosure of which is incorporated herein by reference, discloses an improved frame and suspension system which cushions the occupant and provides better maneuverability.
While these improved frame and suspension systems have contributed to the comfort of the occupant, continued development of wheelchairs and their associated suspension systems has been towards suspension systems that continue to improve the ride and maneuverability of wheelchairs while remaining relatively simple and thus cost effective.